This invention relates to an axial flow type combine in which one or more rotors or coacting concaves are mounted longitudinally of the axis of the combine. Combines of this type are relatively expensive and especially in order to justify a substantial investment in a combine, it is desirable that the same be capable of harvesting a relatively wide variety of crop products. For example, the largest size of product normally harvested by a combine of this type is corn, whereby the kernels of corn are threshed or separated from the cobs, stalks, and leaves or blades, while the normally smallest size of product conventionally harvested by a combine of this type comprises alfalfa and clover, the seeds of which are very small. Concaves employed in so-called universal type combines of the kind referred to comprise a series of bars which extend longitudinally in the threshing compartment of the combine and a series of longitudinally spaced curved wires extend transversely through said bars to provide openings through which threshed material passes and is received by a grain pan beneath the concave, said pan discharging onto a suitable sieve unit incident to completing the separation of the product material from chaff and other waste material.
In view of the fact that rotors employed in this type of combine have rasp bars thereon which extend longitudinally of the rotors and coact with the bars of the concave to effect the disintegration of stalks and stems of the crop material in addition to threshing the seeds or kernels which are the desired crop material, it is essential that such rasp bars be of a very rugged nature and the bars of the concave similarly must be very rugged. Operating prime movers of high horsepower capacity, usually diesel engines, drive the rotors at relatively high speed in order to suitably handle substantial bulkage of the harvested crop material which is delivered to the threshing compartment by the header and elevator of the combine without choking or unduly impeding the speed of operation of the combine and especially the rotor in the threshing compartment. Further, in combines of this type, recent developments therein have included the employment of auger means on the forward end of the rotor to assist in feeding the cut crop material to the threshing compartment and the engagement of such auger means with the crop material produces at least a limited amount of threshing of the desired grain or kernels. Such threshed material from this source as well as that produced by engagement of the rotor and rasp bars with the concave has been found to be subject to damage when threshed kernels or grain are contacted by the rasp bars and this is undesirable.
For readily understanding the type of combine to which the present invention pertains, attention is directed to U.S. Pat. No. 3,696,815, dated Oct. 10, 1972, in the name of Edward W. Rowland-Hill, in which a coacting rotor and concave are illustrated in a multiple-type rotor combine, the concaves having a certain arrangement of wires extending between the bars thereof. Also, U.S. Pat. No. 3,734,103, dated May 22, 1973, in the name of Bernard C. Mathews, shows a rotor and concave in which the concave is provided with bars of a plurality of different sizes and the rotor extends transversely to the longitudinal axis of the combine, the axis of the concave also similarly extending transversely to said combine axis. This structure represents a somewhat earlier standard type of combine rather widely used prior to the advent of the axial flow type combine to which the present invention pertains.
U.S. Pat. No. 3,742,686, dated July 3, 1973, also in the name of Edward W. Rowland-Hill, illustrates a twin type rotor and concave combine which are of the axial flow type, said patent further illustrating upper concaved walls for the twin threshing compartments which include diagonally extending ribs that assist in moving the crop material longitudinally within the threshing compartment to effect more efficient threshing than if such longitudinal movement was not effected.
It will be seen that in the combines of the type illustrated in the aforementioned prior patents, only a single row of wires are employed in the concaves and the arrangement of wires used therein necessarily must serve to accommodate the entire range of sizes of crop materials which are to be threshed by said combines. Under such circumstances, there is no special attempt made to discharge the initially threshed material, either effected by the augers or otherwise, so as to remove the same from damaging engagement by the threshing apparatus and this it has been found that combines of this type are susceptible to effecting damage of at least some of the threshing crop material.
There also are combines of the earlier standard type referred to above which employ a rotor and concave which extend transversely to the longitudinal axis of the combine and in which a row of upper wires are included in the concave and, in addition, a second row of wires of the same diameter as the upper wires are arranged in a row below the upper row but no movement of the material being threshed in a direction parallel to the axis of the rotor and concave is possible, the lower row of wires being provided solely for attempting to adapt the concave to the threshing of different crops under various crop conditions.